Radio broadcast distributing system



March 16 1926.

E. E. CLEMENT RADIOBROADCAST DISTBIBUTNG SYSTEM Original' Filed Jan. 5151925 Patented Mar. 16, 1926.

UNITED STATES 1,577,109 PATENT OFFICE.

EDWARD E. CLEMENT, 0F WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO EDWARD F. CQLLADAY, OF WASHINGTON, DISTRICT 0F COLUMBIA.

RADIO BROADCAST DISTRIBUTING SYSTEM.

Application led January 31, 1925, Serial No. 6,071. Renewed February 11, 1926.

To all fui-kom it may concer-12:

Be it known that I, EDWARD E. CLEMENT, a citizen of the United States, residing at vWashington, in the District of Columbia, have invented certain new and useful Improvements in Radio Broadcast Distributing Systems, of which the following is a specification, reference being had therein to the accompanying drawings.

My invention relates to systems of radio broadcast distribution and has for its object the organization of a system capable of giving service to subscribers in re ional groups, which may be related to eacli other by a general organization corresponding to the long distance telephone organization.

I attain my object by relating my subscribers in each area to one or more local central oces, by means of wired circuits, which may conveniently be telephone line circuits. Each subscriber is provided with a standardized form of receiving radiophone, and each central oilice is also provided with receiving radiophones, but much more elaborate and powerful than those at the subscribers stations. Local service, that is to say, local broadcasting, is received by the subscriber direct but when he desires any station except those that are listed as local, he secures a long distance connection through his line Wires to a central oflice radio receiving set capable of picking up and receiving the station he Wants. The subscribers instrument may conveniently be a single tube regenerative set with common battery connections, taking all its current supply over the subscribers wired circuit.

The central oilice radio sets may conveniently be superheterodynes, or the equivalent thereof, capable of receiving from distant stations and transforming the carrier wave length so as to relay or retransmit the original modulations over the subscribers line on a long carrier wave, preferably at superaudio frequency, such as 30 to 60 kc. per second.

The advantages of this arrangement will be apparent on brief consideration. 'Asingle tube set is usually suicient to give excellent results with local broadcasting, and by us ing a dynamic receiver, it is even; possible to operate therewith amoderately loud table talker or loud speaker. For distance work, lthe antenna or equivalent -Wave collector irs unnecessary, and the nPut Sigle-s, C'Qnaisd.

through a tuned coupler to the line circuit. The same tube detector in the subscribers set then receives the distant signals on long waves, without the necessity of elaborate tunmg on the part of the subscriber. For the local service, since no operators are required, a Hat rate may be charged; but the long distance service is strictly comparable to the long distance service in the telephone exchange, and calls for toll charges apportioned t0 the amount of service rendered, as well as the investment involved.

My invention is illustrated in the accompanying drawings, in which:

Fig. 1 is a diagram of a subscribers station.

Fig. 2 is a connected diagram of the central oilice end of the subscribers wired line circuit, showing terminal devices and switching means therefor.

Fig. 3 is a diagram showing a subscribers radio receiver of the local battery type adapted to be substituted for that of Fig. 1.

Referring to the drawings, Figs. 1 and 2 are to be read together, the dotted lines aa and bb in Figs. 1 and 2 being spaced apart to indicate distance between the subscribers station and the central oilice.

Fig. 1 represents a subscribers instrument. 1 is a detector tube with the usual vfilament 2, grid 3 and plate 4. 5 and 6 are rheostats, 7 is a choke coil, 8 is a telephone transmitter of standard type adapted to be bridged across the line wires 9 and 10 by the push button or key 11, which however, opens as soon as the pressure is removed from it. 12 is the subscribers headphone, 13 is a loop antenna for local receiving, 14 is a tickler loop or regenerative coil, 15 is the usual tuning condenser across the loop, 16-17 is a coupler for connecting the instrument to line for long distance receiving. 18 and 19 are tuning condensers for the long distance circuit, 20 and 21 are radio frequency choke coils included in the branch of the ordinary telephone set 22, and 23 is a gang switch adapted to connect the instrument for either long distance or local receivingto'the telephone line wires 9-16, or to disconnect it entirely therefrom, at will. There 'are no batteries 'at the subscribers station, yall energy 4for all purposes being 'supplied over the .metallic circuitA 9- 10, from the telephone exchange central oiiice Shown.. is. lg- 2:

Fig. 2 shows one telephone line 9-10 with the switching terminals in the form of springjacks J-J, a line relay L, battery B, cut-off relay C, a signal lamp S. These elements of the line, as shown, are all old and well understood, and for the purpose of connecting this line with others for telephonie use, standard lVestern Electric No. 1 switchboard cord circuits are supposed to be employed, which however, are not shown separately herein. The line 9-10, and any number of other lines assumed to be taking radio service, must be supplied with centralized current during operation of their radiophones without keeping their signal lamps S burning, this applying to both local and long distance service. For local service no other connection is required at the central office, but for long distance, that is to say, for receiving from distant stations, the subscribers line is connected at the central ofiice through an amplifier or relay device 37, individual to the line, to a receiving instrumcnt 60, the plate circuit of the amplifier 37 being supplied from a battery B2 while the filament circuit is supplied from a battery B3 controlled through a switch 30. The connection of the line with the set 60 is shown in Fig. 2 as established by means of keys K-K which may be left normally closed, because radio frequency condensers are included in the circuits. In such case the suhscriber can secure long distance service by merely turning his own switch into the proper position and signaling the operator at the central office to close his filament switch 30 which signal is given by operation of the key 11 to flash his line lamp. However, this permanent connection would give him access to only one central receiver, and he would be limited to the program received from stations selected by the central office operators. In order to give him a wider choice, I have indicated also interchangeable switching means consisting of multiple keys Kew-K3 for connection with busses 26-27 and 28-29, which typify any desired number of program busses of different receiving instruments, the different keys K, K2, etc. being actuated by an `operator in response to request made telephonically over the line wire.

The use of the manually operated switching keys K, K', etc. is here shown mainly for the sake of simplicity of disclosure, it being understood that any known or other suitable switching means may be used instead, such for example as the automatic switching means shown and described in my copending application Serial No. 7 54,406, filed December 6, 1924.

The receiver or receivers such as 60 (Fig. 2) at the central station may be of any known or other suitable form capable of receiving radio broadcast matter and relaying it onto the busses 24-25 with amplified or increased power and in the form of a modulated carrier wave of a frequency suitable for line transmission. The preferred form is that of a. superheterodyne receiver such as shown and described in Patent No. 1,522,362, granted to me January 6, 1925.

For the purpose of originating broadcast matter at the central station an oscillator 61 and modulating microphone 62 are connected with the receiving and relaying apparatus 60. In the case of the use of a receiver and relay apparatus of the superheterodyne type the connection would be made by inductively coupling the output circuit of the oscillator 61 with the input or detector circuit ot the superheterodyne in place of the antenna circuit, as will be well understood by those skilled in the art; and as is shown in the prior patent above referred to.

For simplicity in operation it is preferable to maintain the line carrier at a substantially constant frequency, the subscriber sharpening up the tuning, if necessary, by adjustment of the variable condensers 18-19, (Fig. 1).

Where the subscribers apparatus of Fig. 3 is substituted for that of Fig. 1, the operation is the same as that of Fig. 1, except that the supply of current for the filament and plate circuit or circuits is furnished from a local source. In other words, the subscribers radio receiver 63 may be of any known or other type capable of receiving both long and short waves, the coupling to the line 9-10 being effected through the same tuned coupling connection 16-17 and 18-19, by throwing the switch 64, corresponding to the switch 23 of Fig. 1, from the antenna and ground connection, to the tuned coupler connection, thus making the necessary change of tuning automatic in response to the switching off of the input circuit of the receiver from the antenna to the line.

I do not claim herein the use of the amplitier per line except in the system shown, the same being claimed in my copending applications, Serial No. 746,357, filed October 28, 1924; Seria-1 No. 913, filed January 6, 1925; Serial No. 89,410, filed February 19, 1926, as a division of the application Serial No. 739,832, filed September 25, 1924.

That I claim is:

1. In a radiophone system of broadcast distribution, a central station and subscribers stations connected thereto by line wires, a radiophone receiving set at each subscribers station and an antenna therefor, amplifying means at the central station for each subscribers line, means at the central station for supplying carrier current of long Wave length to the said lines through their respective amplifying means, means for operatively connecting the input circuit of the subscribers radio receiving set with either the antenna or the line and means operable upon the switching of said input circuit from the antenna to the line t-o automatically change the tuning of said receiving set from short wave lengths to long wave lengths.

2. In a system of radio broadcast distribution, a central station and subscribers stations connected thereto by line Wires, a radiophone receiving set at each subscribers station and an antenna therefor, amplifying means at the central station for each subscribers line, means at the central station for supplying carrier current to said lines through their respective amplifying means, and means for connecting the subscribers receiving set with either the antenna or the line.

In a system of radio broadcast distribution, a central station and subscribers stations connected thereto by line Wires, a radiophone receiving set at each subscribers station and an antenna therefor, amplifying means at the central station for each subscribers line, means at the central station for electrically transmittingr broadcast matter over said lines through their respective amplifying means, and means for connecting the subscribers receiving set with either the antenna or the line.

4. In a system of radio broadcast distribution, a central station and subscribers stations connected thereto by line wires, a radiophone receiving set at each subscribers station and an antenna therefor, amplifying means at the central station for each subscribers line, a plurality of means at the central station for supplying each with a different electrically transmitted broadcast program, means for selectively connecting a line through its amplifying means with any 011e of said supply means and means for connecting the subscribers receiving set with either the antenna or the line.

5.' Ina system of radio broadcast distribution, a central station and subscribers stations connected thereto by line wires, a radiophone receiving set at each subscribers station andan antenna therefor, amplifying means at the central station for each subscribers line, means at the central station for supplying broadcast matter in a form suitable for wire transmission, operators switching means at the central station for switching a subscribers line onto said supply means through its individual amplifying means, operators switching means for interconnecting said subscribers lines, a line signal at the central office for each line, means at each subscribers station for differentially operating said line signal, and means at each subscribers station for switching the radiophone receiving means from the antenna to the line.

6. In a system of radio broadcast distribution, a central station and subscribers stations connected thereto by l-ine Wires, a radiophone receiving set at each subscribers station and an antenna therefor, amplifying means at the central station for each subscribers line, means at the central station for transmitting a low frequency carrier current over the lines through said amplifying means, a low frequency receiving circuit at each subscribers station tuned to said low frequency carrier current, and means at each subscribers station for connecting the input side of the said radio receiving set to either the antenna circuit or through the low frequency tuned receiving circuit to the line.

7 In a system of radio broadcast distribution, a central station and subscribers stations, a radiophone receiving set at each subscribers station and an antenna therefor, a broadcast transmitting device at the central station, an amplifying device for each subscribers station situated at the central office and means at each subscribers station for switching said radiophone set from the antenna to the transmitting device through its individual amplifying device.

In testimony whereof I hereunto aii'ix my signature.

. EDWARD E. CLEMENT. 

